The Wisconsin Alumni Research Foundation (WARF) filed a lawsuit against Apple, claiming the tech giant had used technology that improves processor efficiency that had been invented and patented by University of Wisconsin researchers and inventors.

After looking into the matter, the jury in Madison, Wisconsin, found that the WARF patent was valid and that Apple had infringed it. As such, Apple could face a hefty bill of $862 million in damages.

The patent, which covers a method for improving processor efficiency, is entitled “Table based data speculation circuit for parallel processing computer” and was granted to WARF in 1998. Apple tried to convince the US Patent and Trademark Office to review the patent’s validity, but without success.

Cupertino, California-based Apple denied any infringement and argued the patent is invalid, according to court papers. Apple previously tried to convince the U.S. Patent and Trademark Office to review the patent’s validity, but in April the agency rejected the bid.

According to a recent ruling by U.S. District Judge William Conley, who is presiding over the case, Apple could be liable for up to $862.4 million in damages.

Now that the jury has ruled in WARF’s favour, the trial will move to the second phase, which is determining the damages owed. There will also be a third trial to determine whether Apple wilfully infringed the patent, and, if this were judged to be the case, it would seriously affect the damages bill.

WARF also filed a second lawsuit against Apple last month using the same patent, alleging the company had used the same technology in its A9 and A9X chip that powers the iPhones and iPad Pro.